Investigation of steps of ferric leaching and biooxidation at the recovery of gold from sulfide concentrate

We examined the ferric leaching and biooxidation steps in a two-step biooxidation process of a gold-bearing sulfide concentrate containing pyrrhotite, arsenopyrite and pyrite. Ferric leaching of the concentrate (pulp density at 200 g/L) for 2 hours at 70°C at pH 1.4 by ferric sulfate solution (initial concentration at 35.6 g/L), which was obtained by microbial oxidation of ferrous sulfate allowed to oxidize 20.4% of arsenopyrite and 52.1% of sulfur. The most effective biooxidation of ferric leached concentrate was observed at 45°C in the presence of yeast extract. Oxidation of the sulfide concentrate in a two-step process proceeded more efficiently than in one-step. In a two-step mode, gold extraction from the residue was 10% higher and the content of elemental sulfur was two times lower than in a one-step process.